predicting the weather is easy

Predicting the weather is easy, just observe the chemical process. Your plans to leave the house or stay at home depend on the results of the weather forecast. If your prediction fails, you will get soaked, if you are rigth, you will provide an umbrella before it rains. – Weather forecast is very important in our life. Your plan for today, is it going out or staying at home, going out in a two-wheeled or four-wheeled vehicle? Planning, possibly, was determined by the weather forecast of the Meteorological Agency.

Before making a weather forecast, a meteorologist must fully understand what causes and affects weather conditions. If he does not understand it then he is just a clairvoyant like the supporters who predict someone’s fate.

Weather is an important part of our lives. Your plans for the day (what you wear, where you go) may be determined by a meteorologist’s weather forecast. Before making such predictions, however, a meteorologist must have an understanding of what causes and affects weather conditions.

In this project, you will study several weather events and determine the chemical nature of each. Clouds, for instance, are one of the many wonders of nature, and, in this first experiment, you will discover the mystery of their formation and disappearance. You will also look at the energy and phase changes involved in the formation of dew and frost. And the laws that determine how gases behave will be used to explain some weather conditions.

Learning Objective

To determine what causes clouds to form and to dissipate (to separate or break up).


glass soda bottle




1-foot (30-cm) piece of aquarium tubing

modelling clay

2 or 3 books

desk lamp

masking tape

sheet of black construction paper


1. Rinse the inside of the soda bottle with water.

2. Pour the water out of the bottle, leaving only enough to cover the bottom of the bottle.

3. Light the candle with the match and allow the candle to burn for 30 seconds.

4. Blow out the candle and hold the smoking wick inside the bottle just long enough for a small puff of smoke to enter it.

5. Insert about 4 inches (10 cm) of one end of the tubing into the middle of the bottle’s mouth.

6. Use modeling clay around the tubing to seal off the mouth of the bottle.

7. Stack the books on a table that is next to a wall.

8. Set the bottle on the stack of books and position the lamp so that it illuminates the bottle from behind but does not shine directly in your eyes.

9. Tape the black paper to the wall behind the bottle so that it creates a dark background (see Figure 1.1).

10. Blow hard into the end of the tubing.

11. Seal the end of the tubing by bending it and holding it tightly with your fingers.

12. Observe the contents of the bottle.

13. Quickly release the tubing and immediately observe the bottle’s contents.

14. Repeat the procedure of blowing into the bottle and releasing the tubing several times.


The contents of the bottle look clear when air is blown into the bottle, but releasing the tubing causes the inside of the bottle to look cloudy.


Molecules in a liquid constantly move around and bounce into one another. When a liquid molecule acquires enough energy to break away from the attraction of other molecules in the liquid, it escapes as vapor into the space above the liquid. This process (liquid becoming vapor) is called evaporation and occurs faster as the temperature increases.

Condensation (vapor becoming liquid) is the reverse of this process and occurs faster when the temperature decreases. In this experiment, when air is forced into the bottle, the increase in pressure causes an increase in temperature; thus, more molecules of invisible water vapor are formed. As the air rushes out, the pressure in side the bottle decreases, causing the contents of the bottle to cool; thus, the water vapor changes back into liquid water.

These changes occur rapidly. Water droplets are formed as the water molecules condense and cling to the smoke particles. These droplets are large enough to scatter the light, so the bottle appears cloudy. The cloud dissipates when the water molecules vaporize. The minute smoke particles are too small to scatter the light, so the bottle appears clear.

You can read the other postings of #nature-school.